Wearable Voice-Induced Vibration or Silent Gesture Sensor

ABSTRACT

Disclosed herein are wearable devices, their configurations, and methods of operation that use self-mixing interferometry signals of a self-mixing interferometry sensor to recognize user inputs. The user inputs may include voiced commands or silent gesture commands. The devices may be wearable on the user&#39;s head, with the self-mixing interferometry sensor configured to direct a beam of light toward a location on the user&#39;s head. Skin deformations or vibrations at the location may be caused by the user&#39;s speech or the user&#39;s silent gestures and recognized using the self-mixing interferometry signal. The self-mixing interferometry signals may be used for bioauthentication and/or audio conditioning of received sound or voice inputs to a microphone.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a nonprovisional of and claims the benefit under 35U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/852,481,filed May 24, 2019, entitled “SMI-Based Wearable Voice-Induced Vibrationand Silent Gesture Sensor,” the contents of which are incorporatedherein by reference as if fully disclosed herein.

FIELD

The present disclosure generally relates to wearable electronic devices.The wearable electronic devices are equipped with self-mixinginterferometry sensors for detection of user inputs and/or user inputcommands. The self-mixing interferometry sensors may detect the userinputs by detecting skin deformations or skin vibrations at one or morelocations on a user's head. The skin deformations or skin vibrations maybe caused by a user's voiced or silent speech or head motion.

BACKGROUND

Wearable electronic devices, such as smart watches or headphones, areoften configured to receive user inputs or commands by detecting auser's voice, or a user's press at a button or on an input screen. Thevoiced input command may be received by a microphone of the wearableelectronic device.

Each of these input processes has potential limitations. Voicerecognition software must distinguish the user's or wearer's voice frombackground noise or voices of others, and press or force inputs requirea user's hands to be free. Also, a user may be unable to input a commandto the wearable electronic device without being heard.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription section. This summary is not intended to identify keyfeatures or essential features of the claimed subject matter, nor is itintended to be used as an aid in determining the scope of the claimedsubject matter.

Disclosed herein are wearable electronic devices and user inputdetection systems for wearable electronic devices. The wearableelectronic devices (or “wearable devices”, or “devices”) may be equippedwith one or more self-mixing interferometry sensors operable to detect auser input or user command by detecting skin deformation or skinvibrations at a location on the user, such as on the head of the user.

More specifically, described herein is a wearable device that includes:a frame configured to attach the wearable device to a user; aself-mixing interferometry sensor mounted to the frame and configured toemit a beam of light; and a command interpreter configured to receive aself-mixing interferometry signal from the self-mixing interferometrysensor. The frame may be configured to direct the beam of light towardthe head of the user. The self-mixing interferometry signal may includeskin deformation information. The command interpreter may be configuredto identify a command encoded in the skin deformation information.

In additional and/or alternative embodiments, the skin deformationinformation may include skin vibration information. The device may beconfigured as an earbud that also includes a microphone and an in-earspeaker. The self-mixing interferometry sensor may direct the beam oflight toward a location in an ear of the user, and the commandinterpreter may be operable to identify a voiced command of the userusing the skin vibration information.

In additional and/or alternative embodiments, the skin deformationinformation may include skin vibration information. The device may beconfigured as an eyeglasses set, with the self-mixing interferometrysensor mounted to an arm of the eyeglasses set. The self-mixinginterferometry sensor may direct the beam of light toward a locationproximate to the temporal bone of the user. The command interpreter maybe operable to identify a voiced command of the user based on the skinvibration information.

In additional and/or alternative embodiments, skin deformationinformation may include temporomandibular joint movement information.The device may be configured as a headphone, with at least oneself-mixing interferometry sensor mounted on the headphone to direct thebeam of light toward a location on the user's head proximate to thetemporomandibular joint of the user. The command interpreter may beoperable to identify the temporomandibular joint movement information asa silent gesture command of the user.

In additional and/or alternative embodiments, the skin deformationinformation may include temporomandibular joint movement information.The device may be configured as a visual display headset, with at leasta first and a second self-mixing interferometry sensor. The firstself-mixing interferometry sensor may direct its beam of light toward alocation on the user's head proximate to a temporomandibular joint ofthe user, and the second self-mixing interferometry sensor may directits beam of light toward a location on the user's head proximate to theparietal bone. The command interpreter may be configured to receiverespective first and second self-mixing interferometry signals from thefirst and second self-mixing interferometry sensors. The commandinterpreter may be configured to detect a silent gesture command of theuser using the first self-mixing interferometry signal and to detect avoiced command of the user using the second self-mixing interferometrysignal.

Also described herein is a device that may include: a head-mountableframe that is configured to be worn by a user; a self-mixinginterferometry sensor mounted to the head-mountable frame and operableto emit a beam of light toward a location on the user's head; amicrophone; a command interpreter configured to receive an output of themicrophone and recognize a voiced command of the user; and abioauthentication circuit configured to authenticate the voiced commandusing a self-mixing interferometry signal of the self-mixinginterferometry sensor.

In additional and/or alternative embodiments, the self-mixinginterferometry signal may include skin deformation information. Thebioauthentication circuit may be operable to detect, using at least theskin deformation information, that the user was speaking during a timeinterval of the received output of the microphone and authenticate thevoiced command using the detection. The authentication of the voicedcommand may include detecting a correlation between the voiced commandof the user and a voice pattern of the user detected in the skindeformation information.

In some embodiments, the device may be an earbud that includes an in-earspeaker and a radio transmitter. The device may transmit the voicedcommand using the radio transmitter upon authentication of the voicedcommand.

In some embodiments, the device may be a headphone, and the location onthe user's head may be proximate to at least one of a temporal bone andthe parietal bone of the user. The device may transmit the voicedcommand using the radio transmitter upon authentication of the voicedcommand.

Also described herein is a device that may include: a head-mountableframe configured to be worn by a user; a self-mixing interferometrysensor mounted to the head-mountable frame and operable to emit a beamof light toward a location on the user's head; a microphone configuredto produce an audio signal; and an audio conditioning circuit configuredto modify the audio signal using a self-mixing interferometry signal ofthe self-mixing interferometry sensor.

In any or all of these various embodiments, the beam of light may beproduced by a laser diode. The various embodiments may use a time-domainI/Q analysis of the self-mixing interferometry signal. Such atime-domain I/Q analysis includes applying a sine wave modulation to thelaser diode's bias current. Alternatively or in conjunction, the variousembodiments may use a spectrum analysis of the self-mixinginterferometry signal when a triangle wave modulation is applied to thelaser diode's bias current. In yet another implementation, a constant(D.C.) driving of the laser diode's bias current may also be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements.

FIG. 1 illustrates a self-mixing interferometry sensor emitting acoherent light beam at a location on a head of a user, according to anembodiment.

FIG. 2A illustrates a block diagram of the components of a wearabledevice, in relation to part of a user's head, according to anembodiment.

FIG. 2B illustrates a block diagram of the components of anotherwearable device, in relation to part of a user's head, according to anembodiment.

FIG. 2C illustrates a block diagram of the components of a thirdwearable device, in relation to part of a user's head, according to anembodiment.

FIG. 3A illustrates an ear bud that may use skin deformation or skinvibration detection, according to an embodiment.

FIG. 3B illustrates a headphone apparatus with a component for detectingskin deformation, or skin vibration or movement, according to anembodiment.

FIG. 4A illustrates a VCSEL diode with an integrated intra-cavityphotodetector, according to an embodiment.

FIG. 4B illustrates a VCSEL diode associated with a separatephotodetector, according to an embodiment.

FIG. 4C illustrates a VCSEL diode with an extrinsic, on-chipphotodetector, according to an embodiment.

FIG. 4D illustrates a VCSEL diode with an extrinsic, off-chipphotodetector, according to an embodiment.

FIG. 5 shows time-correlated graphs of a self-mixing interferometrysignal and a corresponding short-time Fourier transform during voicedspeech, according to an embodiment.

FIG. 6 shows time-correlated graphs of a self-mixing interferometrysignal and a corresponding short-time Fourier transform during silentjaw motion, according to an embodiment.

FIG. 7A illustrates a schematic for a self-mixing interferometry lightsource, according to an embodiment.

FIG. 7B illustrates self-mixing of laser light, according to anembodiment.

FIG. 7C illustrates a variation in an interferometric parameter due toself-mixing, according to an embodiment.

FIG. 8A is a flow chart of a spectrum analysis method for determiningdistances from a light source to an object using self-mixinginterferometry, according to an embodiment.

FIG. 8B shows time-correlated graphs of signals that may occur in aself-mixing interferometry sensor, according to an embodiment.

FIG. 8C illustrates a block diagram of a circuit operable to implementthe spectrum analysis method for determining distances from a lightsource to an object using self-mixing interferometry, according to anembodiment.

FIG. 9A is a flow chart of a time domain method for determiningdistances from a light source to an object using self-mixinginterferometry, according to an embodiment.

FIGS. 9B-C show time-correlated graphs of signals that may occur in aself-mixing interferometry sensor, according to an embodiment.

FIG. 10 illustrates a block diagram of a circuit operable to implementthe time domain method for determining distances from a light source toan object using self-mixing interferometry, according to an embodiment.

FIG. 11 illustrates a block diagram of an electronic device that isconfigured to detect user input, according to an embodiment.

The use of cross-hatching or shading in the accompanying figures isgenerally provided to clarify the boundaries between adjacent elementsand also to facilitate legibility of the figures. Accordingly, neitherthe presence nor the absence of cross-hatching or shading conveys orindicates any preference or requirement for particular materials,material properties, element proportions, element dimensions,commonalities of similarly illustrated elements, or any othercharacteristic, attribute, or property for any element illustrated inthe accompanying figures.

Additionally, it should be understood that the proportions anddimensions (either relative or absolute) of the various features andelements (and collections and groupings thereof) and the boundaries,separations, and positional relationships presented therebetween, areprovided in the accompanying figures merely to facilitate anunderstanding of the various embodiments described herein and,accordingly, may not necessarily be presented or illustrated to scale,and are not intended to indicate any preference or requirement for anillustrated embodiment to the exclusion of embodiments described withreference thereto.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodimentsillustrated in the accompanying drawings. It should be understood thatthe following description is not intended to limit the embodiments toone preferred embodiment. To the contrary, it is intended to coveralternatives, modifications, and equivalents as can be included withinthe spirit and scope of the described embodiments as defined by theappended claims.

The embodiments described herein are directed to wearable devices thatcan detect and respond to user inputs. The user inputs may includeeither or both of voiced (audible) commands or silent (inaudible)gesture commands of a user. As used herein, a “command,” whether voicedor a silent gesture, is to be understood as any of: a user instructionto the device to change the device's operation, an input of data orother information to the device by the user, or another user input toaffect the state of the wearable device itself or of an associatedelectronic device. The embodiments described herein may also be used torecord audible or inaudible communications other than commands. Thewearable device may include a self-mixing interferometry sensor thatuses self-mixing interferometry to detect the voiced or silent gesturecommands, or other voiced or silent communications.

In self-mixing interferometry, a beam of light (visible or invisible) isemitted by a light source of the self-mixing interferometry sensortoward an object. Reflections or backscatters of the emitted beam oflight from an object may be received in the light source and cause thelight source to enter an altered steady state in which the emitted lightis different from light emitted without received reflections. As thedistance or displacement of the object from the self-mixinginterferometry sensor varies, corresponding variations in the alteredstate of the self-mixing interferometry sensor are induced. Theseinduced alterations produce detectable variations in a signal of theself-mixing interferometry sensor that allow the distance, displacement,motion, velocity, or other parameters of the object to be determined.

In various embodiments described herein, the wearable device may be wornor attached to a user, such as on the user's head. The user's voiced orsilent gesture commands may induce skin deformations, such as skinvibrations. For example, audible speech by the user may induce skinvibrations at one or more locations on the scalp or head of the user. Asilent gesture of the user, such as inaudibly forming a word with thejaw and tongue without exhaling, may induce skin deformations at one ormore locations on the scalp or head of the user. The skin deformationsmay be detected by a self-mixing interferometry sensor mounted on aframe of the wearable device.

Specific embodiments described in further detail below include amicrophone equipped earbud, in which the self-mixing interferometrysensor detects the user's speech or voice based on skin vibrations at alocation in the user's ear. In a variation, the earbud may not have aconventional microphone. Instead, the self-mixing interferometry sensormay function for detecting sound inputs. In a second embodiment, an overthe ear(s) headphone may include one or multiple self-mixinginterferometry sensors that may detect the user's voiced commands orsilent gestures from skin deformations at locations proximate to theparietal bone, one of the temporal bones, one of the temporomandibularjoints, or another location on the user's head. In a third embodiment,an eyeglass frame may include a self-mixing interferometry sensor thatmay detect skin deformations proximate to the temporal bone. A fourthembodiment relates to a visual display headset, such as may be used by amixed reality, an augmented reality, or virtual reality (AR/VR) userheadset. The AR/VR headset may include multiple self-mixinginterferometry sensors that may detect the user's voiced commands orsilent gestures from skin deformations at locations proximate to theparietal bone, one of the temporal bones, one of the temporomandibularjoints, or another location on the user's head. These embodiments arelisted as examples, and are not intended to limit the embodiments ofthis disclosure.

Detected skin deformations may be used in various ways. One use is torecognize or identify a command, whether it be input to the wearabledevice as a voiced command or as a silent gesture command. Skindeformations such as skin vibrations from voiced commands may becorrelated with a known voice pattern of the user. This can allow thevoiced command to be recognized and accepted by the device even when thevoiced command is not accurately detected by a microphone (such as mayoccur in the presence of background noise).

Another use is for bioauthentication of received commands. As anexample, a self-mixing interferometry sensor may detect skin vibrationswhen the user is speaking, and so allow the device to accept the commandas it is heard by a microphone of the wearable device. If theself-mixing interferometry sensor does not detect skin deformations orskin vibrations above a threshold, the device may ignore an audibleinput detected by its microphone. In this way, the device can disregardunwanted voiced commands not made by the actual user.

In still another use, a self-mixing interferometry signal may be usedfor audio conditioning. For example, a user's speech recorded by amicrophone may contain background noise. A self-mixing interferometrysignal may allow the device to determine the intended voiced command,and can transmit (such as to another person or device) a reduced noiseversion of the voiced command.

These and other embodiments are discussed below with reference to FIGS.1-11. However, those skilled in the art will readily appreciate that thedetailed description given herein with respect to these figures is forexplanatory purposes only and should not be construed as limiting.

FIG. 1 illustrates a block diagram of a system 100 by which a wearableelectronic device may operate to detect user inputs by detecting ormeasuring skin deflections or deformations at a location on a user'sbody. The block diagram of the system 100 is representational only, anddoes not imply any information regarding dimensions or shape of thefeatures shown. Examples of such electronic devices include, but are notlimited to, an earbud, a headphone, an eyeglass frame, or a mixedreality, an augmented reality or virtual reality (AR/VR) headset. Theseexemplary wearable electronic devices will be explained in furtherdetail below in relation to FIGS. 3A-B. The skin deformation may becaused by voiced or silent commands issued by the user to affectoperation of a wearable electronic device.

The wearable electronic device may include a self-mixing interferometrysensor 102. The self-mixing interferometry sensor 102 is configured toemit an outgoing beam of light 106 directed toward a location on auser's head 110. The outgoing beam of light 106 may pass through anoptional collimating or other lens 104 for focusing and/or filteringprior to impinging on a location of the user's head 110. Reflections orbackscatter 108 of the outgoing beam of light 106 from the user's head110 may reflect back into the light source within the self-mixinginterferometry sensor 102 and alter a property of the outgoing emittedbeam of light 106.

In some embodiments, the light source within the self-mixinginterferometry sensor 102 may be a laser diode in which the receivedreflections 108 of the beam of light 106 induce self-mixing interferencewithin the laser diode's lasing cavity. The self-mixing interferenceproduces an altered steady state of operation of the laser diode from astate of operation that would occur in the absence of receivedreflections 108. For example, the emitted optical power of the beam oflight or emitted wavelength may be altered. Such an alteration may bedetectable as a change in an operational parameter (or “interferometricparameter”) of the source of the beam of light 106, or of an associatedelectrical component of the electronic device. A particular type oflaser diode that may be used in a self-mixing interferometry sensor is avertical cavity, surface emitting laser (VCSEL) diode. Structural andoperational details regarding VCSELs are described below. One skilled inthe art will recognize that other types of laser diodes or light sourcesmay be used in the self-mixing interferometry sensors described herein.

Motion of the location on the user's head 110 may be caused by theuser's speech, such as a voiced command, or by a silent gesture of theuser. Examples of locations on the user's head 110 include the skin orscalp proximate to temporomandibular joints, the temporal bones, theparietal bone, or another location. As an example, speech by the usermay cause vibrations in the temporal bones, which in turn may causevibrations in the skin proximate to the temporal bones. The skinvibrations may be detected by the self-mixing interferometry sensor 102of the device.

FIGS. 2A-C show various block diagrams of configurations for wearableelectronic devices. The configurations shown in the block diagrams arerepresentational only, and do not imply any information regardingdimensions or shape of the features shown.

FIG. 2A is a block diagram of a configuration 200 by which a wearableelectronic device 202 may have an attachment 204 to a part of a user'shead 206 in order to receive inputs from the user by detecting skindeformations. The skin deformations may be caused by the user audibly orinaudibly making a voiced command or a silent gesture, or by anothercause related to a user input to the wearable electronic device.

The device 202 may include a self-mixing interferometry (SMI) sensor 210that emits an outgoing beam of light 208 a toward a location on theuser's head 206, and receives reflections 208 b of the outgoing beam oflight 208 a. The reflections 208 b may cause self-mixing interference ina light source, such as a laser diode, of the SMI sensor 210. Theself-mixing interference may be observed in a self-mixing interferometrysignal, and may be associated or correlated with motion of the user'shead 206.

The device 202 may include a command interpreter 212, that may analyzethe self-mixing interferometry signal, such as by the methods describedbelow in relation to FIGS. 7A-10. The command interpreter 212 mayinclude processors and/or other processing circuits to detect skindeformation information, such as distance, displacement, motion orvelocity of the skin at the location on the user's head 206. From theskin deformation information, the command interpreter 212 may be able torecognize a command of the user, whether it be voiced or a silentgesture.

The command interpreter 212 may send instructions or other signals toaffect the state of the device 202, or of an associated device. Forexample, in the case that the device 202 is an earbud speaker/microphonecombination, the instructions may cause the device 202 to reduce avolume produced by the speaker, or may instruct a cellphone linked withthe earbud to dial a person.

FIG. 2B shows a block diagram of an additional and/or alternativeconfiguration 220 that may extend the configuration 200 of FIG. 2A. Theconfiguration 220 includes a wearable device 222 that can attach to auser's head 226 by means of a connection component 224. Particulardevices making use of the configuration 200 will be described below,with two exemplary devices shown in FIGS. 3A-B. As in the configuration200 of FIG. 2A, the device 222 includes a self-mixing interferometry(SMI) sensor 240, as described above, configured to emit a beam of light228 a toward a location on the user's head 226, and receive reflections228 b from the location that may cause a light source in the SMI sensor240 to undergo self-mixing interference. The self-mixing interferencemay be detected in a self-mixing interferometry signal of theself-mixing interferometry sensor 240.

The device 222 further includes a microphone 232 configured to receivesound input 230. The sound input 230 may be a voiced command of theuser, or originate from another sound source, such as another person, amusic source, or from background noise. The microphone 232 may performan initial filtering or signal conditioning on the received sound input230, and may produce a corresponding output signal having an alternateformat, such as a digital encoded format. The microphone 232 allows thedevice 222 to use sensor fusion, in which both the output signal of themicrophone 232 and the self-mixing interferometry signal from the SMIsensor 240 are both used to detect a user input.

The device 222 includes a command interpreter 234 configured to receivea signal output from the microphone 232 and associated with the soundinput 230. The command interpreter 234 may optionally receive aself-mixing interferometry signal from the SMI sensor 240. The commandinterpreter 234 may analyze the microphone's sound signal and apply avoice recognition algorithm to decide if the sound input 230 originatedfrom a person's voice, such as the user's voice. The command interpreter234 may also make a decision about the content in the sound input 230,and determine if they represent a voiced command.

The command interpreter 234 may optionally be configured to analyze theself-mixing interferometry signal from the SMI sensor 240 to determineif the user was speaking during the time interval in which the soundinput 230 was received. The command interpreter 234 may also make adecision, based on skin deformation information in the self-mixinginterferometry signal, about whether the user made either a voicedcommand or a silent gesture command during the time interval when themicrophone received the sound input 230.

The device 222 further includes a bioauthentication circuit 236configured to authenticate whether a voiced command or a silent gesturecommand arose from the user. The bioauthentication circuit 236 may bepart of, or work in conjunction with, a processor 238 included in thedevice 222.

One such authentication may be to accept a voiced command recognized inthe microphone's output signal only if the analysis of the self-mixinginterferometry signal confirms that the user was speaking when themicrophone received the sound input 230. In another type ofauthentication, a voiced command recognized in the microphone's outputsignal is accepted only when it agrees with a voiced command recognizedin skin deformation information of the self-mixing interferometrysignal. These two types of authentication can reduce improper commandentry to the device 222, such as from a recording of the user's voice,or from another person's voice.

In still another authentication, a silent gesture command recognized inskin deformation information of the self-mixing interferometry signalmay be accepted as valid if the sound input 230 occurring concurrentlywith the skin deformation is below a volume threshold, such as when theuser is not speaking and the background noise is low.

The bioauthentication circuit 236, and/or its associated processor 238,may store voice patterns from the user for recognizing and/orauthenticating voiced commands. The voice patterns of the user may havebeen entered into the device 222 during an initial training session, ormay be obtained during usage of the device 222 by use of learningalgorithms. A voice signal recognized in the microphone's output signalmay only be accepted as a valid input command to the device 222 when itis found to match a stored voice pattern of the user.

FIG. 2C shows a block diagram of an additional and/or alternativeconfiguration 250 that may extend the configuration 200 of FIG. 2A or2B. The configuration 250 includes a wearable device 252 that can attachto a user's head 256 by means of a connection component 254. Particulardevices that may make use of the configuration 250 will be describedbelow, with two examples shown in FIGS. 3A-B. As in the configuration200 of FIG. 2A, the device 252 includes a self-mixing interferometry(SMI) sensor 262, as described above, configured to emit a beam of light258 a toward a location on the user's head 256, and receive reflections258 b from the location. The reflections 258 b may cause a light sourcein the SMI sensor 262 to undergo self-mixing interference. Theself-mixing interference may be detected in a self-mixing interferometrysignal of the SMI sensor 262.

As with the device 222, the device 252 includes a microphone 264operable to detect sound input 260, which may be a voiced command of theuser, or originate from another sound source, such as another person, amusic source, or from background noise. The microphone 264 may performan initial filtering or signal conditioning on the received sound input260, and may produce a corresponding output signal having an alternateformat, such as a digital encoded format. The microphone 264 allows thedevice 252 to use sensor fusion, in which both an output signal of themicrophone 264 and the self-mixing interferometry signal from the SMIsensor 262 are both used to detect a user input.

The device 252 includes an audio conditioning circuit 266 configured toreceive both the output signal of the microphone 264 and the self-mixinginterferometry signal from the SMI sensor 262. The audio conditioningcircuit 266 may be part of the processor 268, or may work in conjunctionwith the processor 268 to analyze the output signal of the microphone264 and the self-mixing interferometry signal from the SMI sensor 262.The audio conditioning circuit 266 may perform bioauthenticationoperations, such any of those described above.

The audio conditioning circuit 266 may be configured to perform variousoperations using the combination of the self-mixing interferometrysignal and the output signal of the microphone 264. In one suchoperation, the audio conditioning circuit 266 and/or its associatedprocessor 268 may have stored various voiced commands of the user. Theaudio conditioning circuit 266 may use the self-mixing interferometrysignal and a concurrently received output signal to determine anintended voiced command from among the stored voiced commands of theuser. The matched voiced command may then be transmitted by the audioconditioning circuit 266 and/or its associated processor 268 to anelectronic device associated with the device 252. For example, thedevice 252 may be the earbud 300 described below, and may be linked by aBluetooth connection with a cellphone. By transmitting the matchedvoiced command, noise in the received sound input 260 would not befurther transmitted.

In a second operation, the audio conditioning circuit 266 may determinethat the output signal from the microphone 264 is below an amplitude orvolume threshold. However, the audio conditioning circuit 266 may detectthat the user was making a silent gesture command based on theself-mixing interferometry signal. The silent gesture command may bematched with a stored voiced command of the user, and that stored voicedcommand may be transmitted to an associated electronic device. Forexample, the device 252 may be the earbud 300 below. A user mayinaudibly form words with jaw motions, such the words or numbers of apasscode, to maintain privacy. While only background noise may bedetected by the microphone 264 in the sound input 260, the audioconditioning circuit 266 may detect the formed words in the skindeformation information in the self-mixing interferometry signal. Thenthe stored voiced command may be transmitted to a cellphone linked withthe earbud.

In a third operation, the audio conditioning circuit 266 may use signalprocessing algorithms, such as weighted averaging, applied to aconcurrently received sound input 260 and a self-mixing interferometrysignal. The signal processing may remove noise, strengthen orinterpolate for inaudible sections in the received sound input 260, orperform other operations.

The audio conditioning circuit 266 may perform other or alternativeoperations in addition to or instead of the operations described.

Details of four specific examples of wearable devices that may implementthe configurations described above are now presented, along with furtherprocesses or operations they may perform. However, it is to beunderstood that other wearable devices are within the scope of thisdisclosure.

FIGS. 3A-B show two exemplary wearable electronic devices that may beconfigured to detect and receive user inputs or commands. The userinputs may be voiced commands or silent gestures.

FIG. 3A illustrates a wearable earbud device (or just “earbud”) 300positioned within a user's ear 302. The earbud 300 may include amicrophone 304 contained in a tubular housing extending from the user'sear toward the user's mouth (along a portion of the user's face). Themicrophone 304 may use any sufficiently compact technology, such as apiezoelectric or other technology, to be contained within an earbud andbe operable to detect and receive voice and audio sounds. The earbud 300may include a middle section 305 configured to lodge in the opening ofthe user's ear canal. The middle section 305 may include an in-earspeaker configured to direct sound into a user's ear canal. The middlesection 305 may also include a radio transmitter/receiver operable totransmit voice or audio signals to another device, such as the user'scellphone. The radio transmitter/receiver may also receiveelectromagnetic signals (such as Bluetooth or another radio frequencytransmission technology) modulated to carry voice or audio signals, andcause the in-ear speaker to produce such voice or audio signals.

The earbud 300 may also contain a self-mixing interferometry sensor 306configured so that when the earbud 300 is worn, the self-mixinginterferometry sensor 306 is positioned to direct a beam of light towarda location 308 in the ear of the user. In some embodiments, the location308 is such that there is minimal tissue between the self-mixinginterferometry sensor and the user's skull. The positioning of theself-mixing interferometry sensor 306 on the earbud 300 may beadjustable by the user to improve detection by the self-mixinginterferometry sensor 306 of skin deformation, which may include skinvibrations.

In such embodiments, when a user speaks, voice-induced vibrations mayoccur in the skull of the user, which may cause corresponding skinvibrations at the location 308. Skin vibrations may be detected atlocation 308 by the self-mixing interferometry sensor 306 based onself-mixing interference, induced by the skin vibrations, in a beam oflight emitted by the self-mixing interferometry sensor 306.

As the skin vibrations at the location 308 may include vibrationsinduced by other sources than the user's speech, the detected skinvibrations may be analyzed by a processing circuitry (not shown) in theearbud 300 to detect information in the skin vibrations that are inducedby the user's speech. Such an analysis may include comparisons of theskin vibrations to one or more voice patterns or stored voiced commandsof the user. Such voice patterns may include those of common voicedcommands.

The earbud 300 may implement any of the bioauthentication operationsdescribed above. The earbud 300 may additionally and/or alternativelyimplement any of the audio conditioning operations described above. Themiddle section 305 may include such electronic circuits as needed toperform such operations, and may contain a battery to supply power tothe microphone 304 and such other electronic circuits.

FIG. 3B shows a second embodiment of a wearable device 320 that may useself-mixing interferometry sensors as part of detecting user inputs. Thewearable device 320 is a headphone device 320 that may fit on a user'shead 322. The headphone device 320 includes at least one over-earspeaker cup 326. The headphone device 320 is attached to the user's head322 by a flexible band 328.

The headphone device 320 may include multiple self-mixing interferometrysensors 324 a-d to detect skin deformations at multiple locations on theuser's head 322. Multiple self-mixing interferometry sensors may allowfor correlation of their respective self-mixing interferometry signalsduring a user's voiced commands or silent gesture commands. Theparticular configuration of the self-mixing interferometry sensors 324a-d is exemplary, and is not to be construed as limiting.

The flexible band 328 includes the self-mixing interferometry sensor 324a, and is configured to direct a light beam emitted by the self-mixinginterferometry sensor 324 a toward a portion of the scalp or skin of theuser 322 that is proximate to the parietal bone of the skull of the user322. Audible speech by the user 322 may cause vibrations in the user'sskull that travel to the parietal bone, which may in turn induce skinvibrations at the location at which the self-mixing interferometrysensor 324 a directs its beam of light.

The self-mixing interferometry sensor 324 b may be located in theover-ear speaker cup 326 and be positioned so that its emitted beam oflight is directed to skin proximate to the temporomandibular joint(TMJ). The user 322 may use jaw and tongue motions to form speech,either audibly by exhaling, or inaudibly by not exhaling, during the jawand tongue motions. In either case, a corresponding motion at the TMJcan cause a skin deformation that can be detected by the self-mixinginterferometry sensor 324 b. Thus the signal of self-mixinginterferometry sensor 324 b may be used in detection of both or eitherof voiced commands and silent gesture user inputs. Further, a user'sparticular jaw motions that are not related to a speech or human soundmay be used as a source of inputs. For example, jaw motions to the rightor left, or up or down, may be detectable and interpretable as specificinputs.

The self-mixing interferometry sensor 324 c may be located in theover-ear speaker cup 326 and be positioned so that its emitted beam oflight is directed to skin proximate to the temporal bone of the user322. Audible speech by the user 322 may cause vibrations in the user'sskull that travel to the temporal bone, which may in turn induce skinvibrations at the location at which the self-mixing interferometrysensor 324 c directs its beam of light.

The self-mixing interferometry sensor 324 d may be located in theover-ear speaker cup 326, and may be positioned so that its emitted beamof light is directed to a location in the ear of the user 322, such asthe location 308 in the ear described above in relation to the earbud300. As described above, audible speech by a user may induce skinvibrations at that location which may be detected by the self-mixinginterferometry sensor 324 d.

The headphone device 320 may make use of any combination of self-mixinginterferometry signals of the self-mixing interferometry sensors 324a-d. The headphone device 320 may contain a command interpreter and atleast one of a bioauthentication circuit and an audio conditioningcircuit, as described previously.

Though only the right side over-ear speaker cup 326 is described, oneskilled in the art will recognize that the headphone device 320 mayinclude a similar over-ear speaker cup for the user's left side. Theleft side over-ear speaker cup may have the same, more, or fewerself-mixing interferometry sensors than the four shown for the rightside over-ear speaker cup 326. Also, one skilled in the art will alsorecognize the right side over-ear speaker cup 326 may itself have moreor fewer than the four self-mixing interferometry sensors 324 a-d shownand described.

The headphone device 320 may detect the user's voiced commands from skindeformation information in the signals of the four self-mixinginterferometry sensors 324 a-d. The headphone device 320 may containtransmitter circuitry that allows the headphone device 320 to send thevoiced commands to another device. Thus the headphone device may notneed to include a dedicated microphone.

A third embodiment of a wearable device that may use self-mixinginterferometry sensors as part of detecting user inputs is an eyeglassframe. A self-mixing interferometry sensor may be located on an arm ofthe eyeglass frame and be positioned to emit its beam of light toward alocation on a user's head proximate to the temporal bone. As alreadydescribed, audible speech by the user may induce skin vibrations at thelocation that may be detectable by the self-mixing interferometrysensor.

As described above, information in the detected skin vibration may beused by a command interpreter to determine a voiced command user input.The self-mixing interferometry sensor may be part of a configurationthat includes a command interpreter and a transmitting circuit, such asin the configurations described in relation to FIGS. 2A-C. The eyeglassframe may also include at least one of a bioauthentication circuit andan audio conditioning circuit, as previously described.

In a variation of this third embodiment, the eyeglass frame may includea self-mixing interferometry sensor located on the bridge connecting thetwo lenses, and positioned to direct its light toward the location onthe skin over the frontal bone of the user. Voiced speech by the usermay cause skin vibrations at the location that may be detected by theself-mixing interferometry sensor. The self-mixing interferometry sensoron the bridge may be in lieu of the self-mixing interferometry sensor onthe arm, or in addition to it.

A fourth embodiment of a wearable device that may use self-mixinginterferometry sensors as part of detecting user inputs, such as voicedcommands or silent gesture user inputs, is an augmented reality/virtualreality (AR/VR) headset. Such an AR/VR headset may include visualdisplay goggles positioned in front of the user's eyes. The AR/VRheadset may include one or two over-ear speaker cups, as shown in FIG.3B, to provide voice and audio input the user. Alternatively, the AR/VRheadset may include an earbud component, such as the earbud 300 of FIG.3A to provide voice and audio input to the user.

The AR/VR headset may include multiple self-mixing interferometrysensors. One self-mixing interferometry sensor may be positioned on thevisual display goggles to direct its beam of light toward the skin ofthe user's head overlying the frontal bone.

Another self-mixing interferometry sensor may be located in a flexiblestrap that extends over the top of the user's head, and be positioned todirect its beam of light toward a location on the user's head proximateto the parietal bone. For example, this self-mixing interferometrysensor may be positioned as shown for self-mixing interferometry sensor324 a in FIG. 3B.

The AR/VR headset may have a flexible strap that extends horizontallyaround the user's head and attaches to the visual display goggles.Another self-mixing interferometry sensor may be positioned on such ahorizontal flexible strap so that its beam of light is directed toward alocation on the user's head proximate to the temporal bone.

In embodiments of AR/VR headsets that use earbuds similar to earbuddevice 300 for voice and audio input to the user, the earbud may includea self-mixing interferometry sensor similarly positioned and operable asthe self-mixing interferometry sensor 306 in FIG. 3A. The earbud mayalso be equipped with a microphone, such as microphone 304 of FIG. 3A.

In embodiments of AR/VR headsets that use at least one over-ear speakercup similar to over-ear speaker cup 326, the over-ear speaker cup mayinclude self-mixing interferometry sensors similarly positioned andoperable as self-mixing interferometry sensors 324 b-d. The over-earspeaker cup may have more or fewer than three self-mixing interferometrysensors.

The self-mixing interferometry sensors of the various embodiments maymake use of laser diodes to produce laser light as the emitted beam oflight. The reflections of the beam of light may induce self-mixinginterference in the lasing cavity. The self-mixing interferometry signalarising from the self-mixing interference may be of an electrical oroptical parameter of the laser diode itself, or may be of a photodiode(PD) associated with, or part of, the laser diode. Specific detailsabout, and configurations of, vertical cavity, surface emitting laser(VCSEL) diodes will be presented below in relation to FIGS. 4A-D.However, other types of laser diodes may be used in a self-mixinginterferometry sensor, such as edge emitting lasers, quantum cascadelasers, quantum dot lasers, or another type. While the exemplaryembodiments for detecting user input are described below as includingboth laser diodes and associated PDs, other embodiments may not includean PD. In such other embodiments, the measured interferometric parameterused to determine distance or displacement may be a parameter of thelaser diode itself, such as a junction voltage or current, a powerlevel, or another parameter.

FIGS. 4A-D show exemplary configurations or structures of VCSEL diodesand associated photodetectors (PDs) that may be included in theself-mixing interferometry sensors of various embodiments of wearabledevices. Such self-mixing interferometry sensors may be used as thesource of the beam of light emitted by a self-mixing interferometrysensor in a wearable electronic device, such as the four particularembodiments of wearable devices described above. These configurationsare exemplary, and should not be construed as limiting.

FIG. 4A shows a structure 400 for a VCSEL diode with an intrinsic (or“integrated”) intra-cavity PD. The structure 400 can be formed in asingle semiconductor wafer, and includes a VCSEL diode having an activegain region 404. At forward bias, a bias current 402 I_(BIAS) flowsthrough the VCSEL diode to cause it to emit laser light 406 from its topsurface. A photodetector 410 can be embedded in the bottom distributedBragg reflector mirror of the VCSEL diode to detect the laser light,including laser light that has undergone self-mixing interference (SMI).The photodetector (PD) 410 may be implemented as a resonant cavityphotodetector (RCPD) with a resonance wavelength that is matched to theemission wavelength of the laser. There may be an etch stop layer 408forming a boundary between the VCSEL diode lasing cavity and the PD 410.During emission of laser light 406, in the case that the PD 410 is aresonant cavity photodetector, the PD 410 is reversed biased so that aphotodetector current 412 I_(PD) flows from the resonant cavity PD 410.

During emission of the laser light 406, SMI may occur due to receptionin the cavity of reflections of the laser light 406. The SMI may causevariations in the photodetector current 412 I_(PD) that correlate withdistance or displacement to the location on a user's head at which thereflections arise.

FIG. 4B shows a structure 420 for part of a self-mixing interferometrysensor in which VCSEL diode 422 is used in conjunction with an extrinsicPD 430 located on a separate chip within a self-mixing interferometrysensor. The VCSEL diode 422 emits a beam of laser light 426 a. Theemitted beam of laser light 426 a may traverse a beam splitter and bedirected by components of a focusing system toward location on theuser's head. Reflections of the emitted beam of laser light 426 a fromthe location may be received back into the VCSEL diode 422 and causeSMI. The SMI alters a property of the emitted beam of laser light 426 a,such as the optical power, to a new steady state value.

Some of the altered beam of emitted beam of laser light 426 a isdiverted by the beam splitter 424 to become the diverted beam of laserlight 426 b that is received by the PD 430. The distance between theVCSEL diode 422 and the beam splitter 424 may be on the order of 100 to250 μm, though this is not required. The PD 430 may include a bandpassfilter 428 to eliminate light at wavelengths different from that of thediverted beam of laser light 426 b. An interferometric parameter, suchas current, of the PD 430 may be monitored, and variations therein usedby other components or circuits of the self-mixing interferometry sensorto determine distances from the self-mixing interferometry sensor to areflection source, such as a location on a head of a user of thewearable electronic device.

FIG. 4C shows a structure 440 for part of a self-mixing interferometrysensor having VCSEL diode 442 and an extrinsic, on-chip PD 456. The PD456 may be a RCPD as described above. The RCPD 456 may form an annulardisk around the VCSEL diode 442. In the structure 440, the RCPD 456 maybe positioned over associated reverse biased VCSEL diode 450 having aquantum wells at layer 452 in order to make the fabrication processeasier. In other embodiments, reverse biased VCSELs may not exist andthe RCPD could be in direct contact with the substrate on which theVCSEL is located.

In operation, the VCSEL diode 442 is forward biased so that it emitslaser light beam 446, and bias current, I_(BIAS), 444 flows through it.The associated VCSEL diode 450 is reverse biased to prevent it fromlasing. The laser light beam 446 may be directed toward a location onthe user's head. The laser beam of light may be reflected from thelocation on the user's head during the emission, and cause SMI in theVCSEL diode 442 that alters the optical power of the emitted laser lightbeam 446. Reflections of the altered emitted laser light beam 446 may bediverted by the beam splitter 448 and received by the RCPD 456. Duringemission of the laser light, the RCPD 456 is reverse biased and producesphotodiode current, I_(PD), 454. The photodiode current 454 is generatedin response to the laser light 446 partially reflected from the beamsplitter 448. The photodiode current 454 may vary due to the SMI andsuch variation may be used to determine distances to a reflectionsource, such as a location on a head of a user of the wearableelectronic device.

FIG. 4D shows a structure 460 for part of a self-mixing interferometrysensor having dual emitting VCSEL diode 462 and an extrinsic, off-chipPD 470. During forward bias, a bias current, I_(BIAS) 464, flows and thedual emitting VCSEL diode 462 emits a beam of laser light 466 from itstop surface, which can be directed by components or circuits of aself-mixing interferometry sensor toward a location on a user's headduring emission. The dual emitting VCSEL diode 462 also emits a secondbeam of laser light 468 from a bottom surface toward a PD 470. The dualemitting VCSEL diode 462 may be formed in a first semiconductor chip andjoined to another chip in which the PD 470 is formed, with the joiningsuch that the second beam of laser light 468 enters the PD 470. Aconnecting layer 472 between the two chips may allow the second beam oflaser light 468 to be transmitted to the PD 470.

As in the previous structures, the first beam of laser light 466 may bereflected from the location on the user's head, with the reflectionscausing SMI in the VCSEL diode 462. The SMI may alter both the firstbeam of laser light 466 and the second beam of laser light 468. Thealteration may cause a correlated change in an interferometric parameterof the structure 460, such as the photodetector current, I_(PD), 474 inthe PD 470. Distances or displacements to the location on the user'shead may be determined using the correlated changes, such as describedin relation to FIGS. 7A-10 below.

FIGS. 5 and 6 each show a pair of respective time-correlated graphsbetween a self-mixing interferometry signal and a correspondingshort-time Fourier transform (STFT) of that signal. These figuresillustrate how the wearable devices that make use of self-mixinginterferometry sensors can detect time intervals during which the useris likely to be making a voiced command or a silent gesture input.Detecting such time intervals is useful in both bioauthenticationoperations and for audio conditioning operations, as described above.

FIG. 5 shows two exemplary time-correlated graphs 500 related to aself-mixing interferometry signal produced when a user is speaking. Thetop graph 502 shows an electronic output of the SMI signal itself, whichmay be photodetector output current or voltage, or an interferometricparameter of a laser diode, such as an optical power or bias current.The SMI signal includes voice pattern components that extend aboveapproximately 10 mV. The SMI signal also includes a time interval 504during which the user does not speak, so that the SMI signal onlyincludes a background noise floor. On each side of the time interval 504are representative speech events, shown in boxes.

The bottom graph 508 shows an amplitude plot of a short-time Fouriertransform (STFT) of the SMI signal. During the time interval 504, theamplitude is below a noise threshold 505, whereas during therepresentative speech events the amplitude exceeds the noise threshold505.

As described above in relation to FIGS. 2A-C, time intervals duringwhich the user is speaking or silent are used in bioauthenticationoperations and audio conditioning operations. Such operations may thusapply a STFT to an SMI signal as part of determining that the user isgiving a voiced command.

FIG. 6 shows two exemplary time-correlated graphs 600 related to aself-mixing interferometry signal produced by skin deformations due tojaw motion, such as at a TMJ. The top graph 602 shows an electronicoutput of the SMI signal itself, which may be photodetector outputcurrent or voltage, or an interferometric parameter of a laser diode,such as an optical power or bias current. The SMI signal includespronounced spikes in amplitude at jaw motion events, such as jaw motionevent 603 a.

The bottom graph 604 shows an amplitude plot of a STFT of the SMIsignal. During the jaw motion event 603 a, the STFT shows a pronouncedpeak 603 b that extends above a noise floor 605 so a user's jaw motionevents may be distinguished from background noise. Bioauthenticationand/or audio conditioning operations may apply a STFT to the SMI as partof determining silent gesture commands made by jaw motion of the user.

FIGS. 7A-C illustrate properties of self-mixing interference of coherentlight emitted from a light source. The explanations are intended only todescribe certain aspects of self-mixing interference needed tounderstand the disclosed embodiments. Other aspects of self-mixinginterference will be clear to one skilled in the art.

FIG. 7A illustrates an exemplary configuration of a laser light source700, specifically a VCSEL diode 700, that may be used as part of aself-mixing interferometry sensor. In any type of laser, an input energysource causes a gain material within a cavity to emit coherent light.Mirrors on ends of the cavity feed the light back into the gain materialto cause amplification of the light and to cause the light to becomecoherent and (mostly) have a single wavelength. An aperture in one ofthe mirrors allows transmission of the laser light (e.g., transmissiontoward a location on the surface of a user's head).

In the VCSEL 700, there are two mirrors 702 and 704 on opposite ends ofa cavity 706. The lasing occurs within the cavity 706. In the VCSELdiode 700, the two mirrors 702 and 704 may be implemented as distributedBragg reflectors, which are alternating layers with high and lowrefractive indices. The cavity 706 contains a gain material, which mayinclude multiple doped layers of III-V semiconductors. In one example,the gain material may include AlGaAs, InGaAs, and/or GaAs. The emittedlaser light 710 can be emitted through the topmost layer or surface ofVCSEL diode 700. In some VCSEL diodes, the coherent light is emittedthrough the bottom layer.

FIG. 7B shows a functional diagram of self-mixing interference (or also“optical feedback”) with a laser. In FIG. 7B, the cavity 706 has beenreoriented so that emitted laser light 710 is emitted from the cavity706 to the right. The cavity 706 has a fixed length established atmanufacture. The emitted laser light 710 travels away from the cavity706 until it intersects or impinges on a target, which may be a locationon a user's head, as in the embodiments described in relation to FIGS.3A-B. The gap of distance L from the emission point through the mirror704 of the emitted laser light 710 to the target is termed the feedbackcavity 708. The length L of the feedback cavity 708 is variable as thetarget can move with respect to the VCSEL diode 700.

The emitted laser light 710 is reflected back into the cavity 706 by thetarget 716. The reflected light 712 enters the cavity 706 to coherentlyinteract with the original emitted laser light 710. This results in anew steady state illustrated with the new emitted laser light 714. Theemitted laser light 714 at the new steady state may have characteristics(e.g., a wavelength or power) that differ from what the emitted laserlight 710 would have in the absence of reflection and self-mixinginterference.

FIG. 7C is a graph 720 showing the variation in power of the combinedemitted laser light 714 as a function of the length L of the feedbackcavity 708, i.e., the distance from the emission point through themirror 704 of the emitted laser light 710 to the target. The graphdepicts a predominantly sinusoidal variation with a period of λ/2.Theoretical considerations imply that the variation is given by theproportionality relationship: ΔP∝cos(4πL/λ. This relationship generallyholds in the absence of a strong specular reflection. In the case ofsuch strong specular reflection, the cosine becomes distorted, i.e.,higher harmonics are present in the relationship. However, thepeak-to-peak separation stays at λ/2. For an initially stationarytarget, this relationship can be used to determine that a deflection hasoccurred. In conjunction with other techniques, such as counting of thecompleted number of periods, the range of the deflection may also bedetermined.

Though the graph 720 shows the variation in power of the combinedemitted laser light 714 as a function of the length L of the feedbackcavity 708, similar results and/or graphs may hold for otherinterferometric properties of a VCSEL diode or other type laser diodethat are measured by a self-mixing interferometry sensor.

Measurements of one or more interferometric parameters by a self-mixinginterferometry sensor can be used to infer distances and/ordisplacements of the target 716 from the VCSEL 700. These distance ordisplacement measurements can then be used to detect skin deformationsor skin vibrations, as in the embodiments described above. A firstfamily of embodiments uses a spectrum analysis of a signal of aninterferometric parameter. A variation in the interferometric parameteris produced when an input signal (e.g., a bias current) of the laserdiode is modulated with a triangle wave about a constant current value.The first family of embodiments is described in relation to FIGS. 8A-C.

A second family of embodiments uses time domain filtering anddemodulation of a signal of an interferometric parameter. A variation inthe interferometric parameter is produced when a bias current of thelaser diode is modulated with a sine wave about a constant currentvalue. The second family of embodiments is described in relation toFIGS. 9A-C and 10.

In regard to the first family of embodiments, FIG. 8A is a flowchart ofa spectrum analysis method 800 for determining distances from anself-mixing interferometry sensor to a location on a user's head. Thespectrum analysis method 800 involves applying a triangle wavemodulation to a bias current of a laser diode, and applying separatespectrum analyses to the signal of an interferometric parameter obtainedduring the rising time interval of the triangle wave modulation and tothe signal of the interferometric parameter obtained during the fallingtime interval of the triangle wave modulation. The signal of theinterferometric property may be an output signal of a photodetector,such as an output current or voltage, or it may be a signal of aninterferometric parameter of the VCSEL itself.

FIG. 8B shows three time correlated graphs 860 relating a trianglemodulated laser bias current 862 with the resulting laser wavelength 864and the resulting signal 866 of the measured interferometric parameter.The graphs 860 in FIG. 8B correspond to a stationary target. While thelaser bias current 862 is shown with equal ascending and descending timeintervals, in some embodiments these time intervals may have differentdurations. The spectrum analysis methods may make use of both the laserbias current 862 and the signal 866 of the measured interferometricparameter. In the case of a non-stationary target, the observedfrequencies in the resulting signal 866 would differ during the risingand falling time intervals of the bias current 862. Distance andvelocity can be obtained by a comparison of the two frequency values.

Returning to FIG. 8A, at stage 802 of the spectrum analysis method 800,an initial signal is generated, such as by a digital or an analog signalgenerator. At stage 806 a the generated initial signal is processed asneeded to produce the triangle modulated laser bias current 862 that isapplied to the VCSEL. The operations of stage 806 a can include, asneeded, operations of digital-to-analog conversion (DAC) (such as whenthe initial signal is an output of a digital step generator), low-passfiltering (such as to remove quantization noise from the DAC), andvoltage-to-current conversion.

The application of the triangle modulated laser bias current 862 to theVCSEL induces a signal 866 in the interferometric parameter. It will beassumed for simplicity of discussion that the signal 866 of theinterferometric parameter is from a photodetector, but in otherembodiments it may be another signal of an interferometric parameterfrom another component. At initial stage 804 of the spectrum analysismethod 800, the signal 866 is received. At stage 806 b, initialprocessing of the signal 866 is performed as needed. Stage 806 b mayinclude high-pass filtering.

At stage 808 the processing unit may equalize the received signals, ifnecessary. For example the signal 866 may include a predominant trianglewaveform component matching the triangle modulated laser bias current862, with a smaller and higher frequency component due to changes in theinterferometric parameter. High-pass filtering may be applied to thesignal 866 to obtain the component signal related to the interferometricparameter. Also, this stage may involve separating the parts of signal866 and the triangle modulated laser bias current 862 corresponding tothe ascending and to the descending time intervals of the trianglemodulated laser bias current 862. The operations may include samplingthe separated information.

At stages 808 and 810, a separate FFT is first performed on the parts ofthe processed form of signal 866 corresponding to the ascending and tothe descending time intervals. Then the two FFT spectra are analyzed atstage 812.

At stage 814, further processing of the FFT spectra can be applied, suchas to remove artifacts and reduce noise. Such further processing caninclude windowing, peak detection, and Gaussian fitting.

At stage 816, from the processed FFT spectra data, information regardingthe skin deformation can be obtained, including an absolute distance,and/or a direction and velocity of the skin deformation or vibration atthe location on the user's head. More specifically, the velocity isdetected in the direction of the laser light.

FIG. 8C shows a block diagram of a system 890 that can implement thespectrum analysis just described in the spectrum analysis method 800. Inthe exemplary system 890 shown, the system 890 includes generating aninitial digital signal and processing it as needed to produce a trianglemodulated laser bias current 862 as an input to a bias current of aVCSEL diode 893. In an illustrative example, an initial step signal (notshown) may be produced by a digital generator to approximate a trianglefunction. The digital output values of the digital generator are used inthe digital-to-analog (DAC) converter 892 a. The resulting voltagesignal may then be filtered by the low-pass filter 892 b to removequantization noise. Alternatively, an analog signal generator can beused to generate an equivalent triangle voltage signal directly. Thefiltered voltage signal then is an input to a voltage-to-currentconverter 892 c to produce the desired triangle modulated laser biascurrent 862 in a form for input to the VCSEL diode 893.

As described above, reflections from the location on the user's head cancause SMI in the VCSEL diode 893 that alter an interferometric parameterof the VCSEL diode 893. This alteration in the interferometric parametermay be measured or inferred, either from a parameter of the VCSEL diode893 itself or from a parameter of an associated photodetector. Thechanges can be measured to produce a signal 866. In the system 890 shownit will be assumed the signal 866 is measured by a photodetector. Forthe triangle modulated laser bias current 862, the signal 866 may be atriangle wave of similar period combined with a smaller and higherfrequency signal related to the changes in the interferometricparameter.

The signal 866 is first passed into the high-pass filter 895 a, whichcan effectively convert the major ascending and descending rampcomponents of the signal 866 to DC offsets. As the signal 866 from aphotodetector may be a current signal, the transimpedance amplifier 895b can produce a corresponding voltage output for further processing.

The voltage output can then be sampled and quantized by theanalog-to-digital conversion (ADC) block 895 c. Before immediatelyapplying a digital FFT to the output of the ADC block 895 c, it can behelpful to apply equalization in order to clear remaining residue of thetriangle signal received by the photodiode, and thus isolate theinterferometric signal. The initial digital signal values from thedigital generator used to produce the triangle modulated laser biascurrent 862 are used as input to the digital high pass filter 894 a toproduce a digital signal to correlate with the output of the ADC block895 c. An adjustable gain can be applied by the digital variable gainblock 894 b to the output of the digital high pass filter 894 a.

The output of the digital variable gain block 894 b is used as one inputto the digital equalizer and subtractor block 896. The other input tothe digital equalizer and subtractor block 896 is the output of the ADCblock 895 c. The two signals are differenced, and used as part of afeedback to adjust the gain provided by the digital variable gain block894 ba.

Once an optimal correlation is obtained by the feedback, an FFT,indicated by block 897, can then be applied to the components of theoutput of the ADC block 895 c corresponding to the rising and descendingof the triangle wave. From the FFT spectra obtained, movement of thelocation on the user's head can be inferred, as discussed above andindicated by block 898.

The second family of embodiments of devices and methods for recognizinga user input or command based on skin deformation or skin vibrationdirectly obtains distance or displacement measurements from the signalof an interferometric parameter and using a time domain based analysis.This family is described in relation to FIGS. 9A-C and 10. The methodsand devices make use of a sinusoidal modulation of a bias current of thelaser diode and detects resulting effects in an interferometricparameter of a photodetector associated with the laser diode.

In this second family of embodiments, a laser light source, such any ofthe VCSELs described in FIGS. 4A-D, is used to direct laser light towardthe location on the user's head. For simplicity of explanation only forthis family of embodiments, the laser light source(s) will be assumed tobe VCSEL(s). One skilled in the art will recognize how the embodimentsmay make use of other types of lasers or light sources that undergoself-mixing interference. In this second family of embodiments, theremay be one or more photodetectors associated with each VCSEL, at leastone of whose output parameters is correlated with a property of theself-mixing of the laser light that arises when some of the laser lightemitted from the VCSEL diode is received back into the VCSEL diode afterreflection from a target. In some embodiments, the photodetector isintegrated as part of the VCSEL, such as in FIG. 4A. In otherembodiments, the photodetector may be separate from the VCSEL, as inFIG. 4B. Instead of, or in addition to, an output of such aphotodetector, some embodiments may measure another interferometricproperty of the VCSEL diode, such as a junction voltage.

The self-mixing interference effect contains at least two contributions:a first contribution from internal an electric field existing within theVCSEL diode and a second contribution from reflections from the targetcoupled back into the VCSEL diode, as indicated in FIG. 4B. The secondcontribution enters the laser cavity phase shifted from the first. Theradian value of the phase shift can be expressed as Δφ=2π[2L mod λ], orequivalently as

${2{\pi \left( {\frac{2L}{\lambda} - \left\lfloor \frac{2L}{\lambda} \right\rfloor} \right)}},$

where Δ is the wavelength of the laser light.

The bias current of a VCSEL diode may be driven by electronics, or othermeans, to include a superimposed sinusoidal modulation component, tohave the form I_(BIAS)∝1+β sin(ω_(m)t), where β is typically less than1, and ω_(m) is the radian modulation frequency. The radian modulationfrequency ω_(m) is much less than the frequency of the laser light. Whena VCSEL diode is driven with such a bias current, the phase of theoptical feedback light returning from the target upon reflection is suchthat Δφ∝a+b sin(ω_(m)t), for constants a and b. Certain specific formsfor constants a and b for some embodiments will be presented below.

When the two contributions coherently interfere inside the laser cavity,the phase shift between them can cause their electric fields tointerfere, either destructively or constructively. As a result, anoutput current of the photodetector can have the form I_(PD)∝[1+δcos(Δφ)] in response to the similarly evolving optical output power ofthe VCSEL diode.

The Fourier series expansion of the function cos(a+b sin(ω_(m)t)) hasthe form

{cos(a+b sin(ω_(m)t))}=J₀ (b) cos(a)−2J₁(b) sin(a)sin(ω_(m)t)+2J₂(b)cos(a)cos(2ω_(m)t)−2J₃(b)sin(a)sin(3ω_(m)t)+higherorder harmonics, where J_(k) indicates the Bessel function of the firstkind of order k. So for the situation above of a sinusoidally modulatedbias current of a VCSEL, the photodetector output current has aharmonics of the radian modulation frequency that can be selected byfiltering, and the respective coefficient values that can be determinedby demodulation, as explained in relation to FIGS. 9A-C and 10 below.

For a target that had an initial distance L₀ from the VCSEL diode, andwhich has undergone a displacement of ΔL from L₀, the constants a and babove in some cases are given by:

a=[4π(L ₀ +ΔL)/λ], and b=[−4πΔλ(L ₀ +ΔL)/λ²].

Certain specific forms of the expansion for I_(PD) may thus be given by:

$I_{PD} \propto {{{Baseband}\mspace{14mu} {Signal}} - {2{J_{1}\left\lbrack {\frac{{- 4}{\pi\Delta\lambda}\; L_{0}}{\lambda^{2}}\left( {1 + \frac{\Delta \; L}{L_{0}}} \right)} \right\rbrack}{\sin \left( \frac{4{\pi\Delta}\; L}{\lambda} \right)}{\sin \left( {\omega_{m}t} \right)}} + {2{J_{2}\left\lbrack {\frac{{- 4}{\pi\Delta\lambda}\; L_{0}}{\lambda^{2}}\left( {1 + \frac{\Delta \; L}{L_{0}}} \right)} \right\rbrack}{\cos \left( \frac{4{\pi\Delta}\; L}{\lambda} \right)}{\cos \left( {2\omega_{m}t} \right)}} - {2{J_{3}\left\lbrack {\frac{{- 4}{\pi\Delta\lambda}\; L_{0}}{\lambda^{2}}\left( {1 + \frac{\Delta \; L}{L_{0}}} \right)} \right\rbrack}{\sin \left( \frac{4{\pi\Delta}\; L}{\lambda} \right)}{\sin \left( {3\omega_{m}t} \right)}} + \ldots}$

By defining a Q-component of I_(PD) as a low pass filtering anddemodulation with respect to the first harmonic, i.e.Q∝Lowpass{I_(PD)×sin(ω_(m)t)}, and an I-component as a low passfiltering and demodulation with respect to the second harmonic, i.e.I∝Lowpass{I_(PD)×cos(ω_(m)t)}, one can obtain a first value

${Q \propto {\sin \left( \frac{4\pi \Delta L}{\lambda} \right)}},$

and a second value

${l \propto {\cos \left( \frac{4\pi \Delta L}{\lambda} \right)}}.$

Then one can use the unwrapping arctan function (that obtains an anglein any of all four quadrants) to obtain the displacement as

${\Delta \; L} = {\frac{\lambda}{4\pi}{{\arctan \left( {Q/I} \right)}.}}$

In a modification of this implementation of the low pass filtering anddemodulation, a Q′-component of I_(PD) can be defined as a low passfiltering and demodulation with respect to the third harmonic, i.e.,Q′∝Lowpass{I_(PD)×sin(3ω_(m)t)}. This can then be used with theI-component derived by filtering and demodulation at the secondharmonic, as above, to obtain a modified first value

${Q^{\prime} \propto {\sin \left( \frac{4{\pi\Delta}\; L}{\lambda} \right)}},$

and the second value

${l \propto {\cos \left( \frac{4\pi \Delta L}{\lambda} \right)}}.$

Then, as before, one can use the unwrapping arctan function (thatobtains an angle in any of all four quadrants) to obtain thedisplacement as

${\Delta \; L} = {\frac{\lambda}{4\pi}{{\arctan \left( {Q/I^{\prime}} \right)}.}}$

This modification makes use of frequency components of I_(PD) separatefrom the original modulation frequency ω_(m) applied to the VCSEL diodebias current I_(BIAS). This may reduce the need for filtering and/orisolation of I_(PD) at the original modulation frequency ω_(m).

In a still further modification, one can use the form of the BasebandSignal (DC signal component) in the expansion above to obtain analternative I-component derived by filtering and demodulation at the DCcomponent:

$I^{\prime} \propto {{\cos \left( \frac{4{\pi\Delta}\; L}{\lambda} \right)}.}$

This alternative I-component can then be used with the Q-component aboveto obtain

${\Delta \; L} = {\frac{\lambda}{4\pi}{{\arctan \left( {Q/I^{\prime}} \right)}.}}$

The low pass filtering and demodulations just discussed can be furtherexplained in relation to FIGS. 9A-C and FIG. 10. FIG. 9A is a flow chartof a method 900 for detecting skin deformation and/or skin vibrationsurface, using distance or displacement measurements.

At block 902, the modulation waveform for the bias current to the VCSELdiode is generated. The generation may involve separately generating adirect current (DC) input signal and a sine wave current input signalwith desired modulation frequency ω_(m) (in radians), and then summingthe two signals to produce I_(BIAS). The two input signals can begenerated either by current sources, or from voltage sources thatproduce I_(BIAS). The generation of the two input signals may initiallybegin using one or more digital generators, such as digital-to-analog(DAC) converters.

At block 904, the generated modulation waveform may be filtered toreduce signal frequency components not at the desired modulationfrequency ω_(m). Such filtering may be a digital filtering applied to adigital sine wave source, or an analog filtering of an analog sine wavecurrent input signal. Filtering may also be applied to the DC signalsource before being summed with the sine wave current input signal.

The generated modulation waveform is applied to I_(BIAS), modifying theVCSEL diode's emitted laser light accordingly. Self-mixing interferencethen may occur due to reflections from the location on the user's head.

At block 906, a photodetector receives the VCSEL diode's laser light,and a corresponding signal produced. The signal may be a photodetectorcurrent, a voltage of the photodetector, or another interferometricproperty. Further, as explained above, the photodetector may beintegrated with the VCSEL diode itself.

Because the bias current of the VCSEL diode was modulated at desiredmodulation frequency ω_(m), it may well be that the receivedphotodetector signal also has a frequency component at ω_(m). At block908, a scaled version of the modulated form of I_(BIAS) and receivedphotodetector signal may be differenced in a differential filtering toreduce cross-talk or other interferences. The result may be adifferenced signal that correlates with the self-mixing interference inthe VCSEL diode's laser light.

At block 910, an I and a Q component of the filtered form of thephotodetector signal are then extracted. These extractions may beperformed by separate mixing (multiplying) of the filtered form of thephotodetector signal with separately generated sinusoidal signals atrespective frequencies ω_(m) and 2ω_(m), as discussed above.Alternatively, the modifications discussed above based on using eitherQ′ or I′ may be used. The mixed signals are then separately low passfiltered.

At block 912, the phase of the I and Q components may be calculatedusing unwrapping arctan function, as described above. An alternativemethod of obtaining the phase may also be used. At block 914, thedisplacement is determined based on the phase, as described above.

FIGS. 9B-C show two time correlated graphs: 920, 930. Graph 920 shows aplot 922 of a bias current I_(BIAS) of a VCSEL diode modulated by a sinewave at a single frequency. The amplitude of the sinusoidal modulationis only for illustration, and need not correspond to amplitudes used inall embodiments. The bias current I_(BIAS) has its sinusoidal variationabout a fixed direct current value, 924.

As a result of the sinusoidal modulation, the output current of aphotodetector receiving the VCSEL's self-mixing laser light undergoes atime variation, shown in the plot 932 in the graph 930. The time axes ofgraphs 926 and 936 are correlated. The plot 932 illustrates that theoutput current of the photodetector varies around a fixed direct currentvalue 934.

The sinusoidally modulated bias current I_(BIAS) and correspondingphotodetector current may arise within the circuit shown in FIG. 10, asnow described. Other circuits may be used to implement the time domainI/Q methods as described, and may produce bias currents and respectivephotodetector currents having respective plots similar to 922 and 932.

FIG. 10 shows an exemplary circuit block diagram that may be used toimplement the third family embodiments. Other circuits may also be used,as would be clear to one skilled in the art. The circuit block diagramof FIG. 10 shows the relationships and connections of certain componentsand sections; other circuits that implement these embodiments may usemore or fewer components. As explained in more detail below, FIG. 10shows components which generate and apply a sinusoidally modulated biascurrent to a VCSEL. The sinusoidal bias current can generate in aphotodetector 1016 an output current depending on the frequency of thesinusoidal bias and the displacement to the target. In the circuit ofFIG. 10, the photodetector's 1016 output current is digitally sampledand then multiplied with a first sinusoid at the frequency of theoriginal sinusoidal modulation of the bias current, and a secondsinusoid at double that original frequency. The two separate multipliedoutputs are then each low pass filtered and the phase calculated.Thereafter the displacement is determined using at least the phase.

The DC voltage generator 1002 is used to generate a constant biasvoltage. A sine wave generator 1004 may produce an approximately singlefrequency sinusoid signal, to be combined with constant voltage. Asshown in FIG. 10, the sine wave generator 1004 is a digital generator,though in other implementations it may produce an analog sine wave. Thelow pass filter 1006A provides filtering of the output of the DC voltagegenerator 1002 to reduce undesired varying of the constant bias voltage.The bandpass filter 1006B can be used to reduce distortion and noise inthe output of the sine wave generator 1004 to reduce noise, quantizationor other distortions, or frequency components of its signal away fromits intended modulation frequency, ω_(m).

The circuit adder 1008 combines the low pass filtered constant biasvoltage and the bandpass filtered sine wave to produce on link 1009 acombined voltage signal which, in the embodiment of FIG. 10, has theform V₀+V_(m) sin(ω_(m)t). This voltage signal is used as an input tothe voltage-to-current converter 1010 to produce a current to drive thelasing action of the VCSEL diode 1014. The current from thevoltage-to-current converter 1010 on the line 1013 can have the formI₀+I_(m) sin(ω_(m)t).

The VCSEL diode 1014 is thus driven to emit a laser light modulated asdescribed above. Reflections of the modulated laser light may then bereceived back within the lasing cavity of VCSEL diode 1014 and causeself-mixing interference. The resulting self-mixing interference lightmay be detected by photodetector 1016. As described above, in such casesthe photocurrent output of the photodetector 1016 on the link 1015 canhave the form: I_(PD)=i₀+i_(m) sin(ω_(m)t)+γ cos(φ₀+φ_(m) sin(ω_(m)t)).As the I/Q components to be used in subsequent stages are based on justthe third term, the first two terms can be removed or reduced by thedifferential transimpedance amplifier and anti-aliasing (DTIA/AA) filter1018. To do such a removal/reduction, a proportional or scaled value ofthe first two terms is produced by the voltage divider 1012. The voltagedivider 1012 can use as input the combined voltage signal on the link1009 produced by the circuit adder 1008. The output of the voltagedivider 1012 on link 1011 can then have the form α(V₀+V_(m)sin(ω_(m)t)). The photodetector current and this output of the voltagedivider 1012 can be the inputs to the DTIA/AA filter 1018. The output ofthe DTIA/AA filter 1018 can then be, at least mostly, proportional tothe third term of the photodetector current.

The output of the DTIA/AA filter 2018 may then be quantized forsubsequent calculation by the analog-to-digital converter (ADC) block1020. Further, the output of the ADC block 1020 may have residual signalcomponent proportional to the sine wave originally generated by the sinewave generator 1004. To filter this residual signal component, theoriginally generated sine wave can be scaled (such as by the indicatedfactor of β) at multiplier block 1024C, and then subtracted from theoutput of ADC block 1020. The filtered output on link 1021 may have theform A+B sin(ω_(m)t)+C cos(2ω_(m)t)+D sin(3ω_(m)t)+ . . . , from theFourier expansion discussed above. The filtered output can then be usedfor extraction of the I/Q components by mixing.

The digital sine wave originally generated by sine wave generator 1004onto link 1007 is mixed (multiplied) by the multiplier block 1024 a withthe filtered output on link 1007. This product is then low pass filteredat block 1028 a to obtain the Q component discussed above.

Also, the originally generated digital sine wave is used as input intothe squaring/filtering block 1026 to produce a digital cosine wave at afrequency double that of the originally produced digital sine wave. Thedigital cosine wave is then mixed (multiplied) at the multipliercomponent 1024 b with the filtered output of the ADC block 1020 on link1021. This product is then low pass filtered at component 1028 b toobtain the I component discussed above.

The Q and the I components are then used by the phase calculationcomponent 1030 to obtain the phase from which the displacement of thetarget can be calculated, as discussed above.

One skilled in the art will appreciate that while the embodiment shownin FIG. 10 makes use of the digital form of the originally generatedsine wave produced by sine wave generator 1004 onto link 1007, in otherembodiments the originally generated sine wave may be an analog signaland mixed with an analog output of the DTIA/AA 1018.

The circuit of FIG. 10 can be adapted to implement the modified I/Qmethod described above that uses Q′∝Lowpass{I_(PD)×sin(3ω_(m)t)}. Somesuch circuit adaptations can include directly generating both mixingsignals sin(2ω_(m)t) and sin(3ω_(m)t), and multiplying each with theoutput of the output of the ADC block 1020, and then applying respectivelow pass filtering, such as by the blocks 1028 a,b. The differential TIAand anti-aliasing filter may then be replaced by a filter to remove orgreatly reduce the entire component of I_(PD) at the original modulationfrequency ω_(m). One skilled in the art will recognize other circuitadaptations for implementing this modified I/Q method.

In additional and/or alternative embodiments, the I/Q time domain basedmethods just described may be used with the spectrum based methods ofthe first family of embodiments. The spectrum methods of the firstfamily can be used at certain times to determine the absolute distanceto the target, and provide a value of L₀. Thereafter, during subsequenttime intervals, any of the various I/Q methods just described may beused to determine ΔL.

In additional and/or alternative embodiments, the spectrum methods basedon triangle wave modulation of a bias current of a VCSEL may be used asa guide for the I/Q time domain methods. The I/Q methods operateoptimally in the case that J₁(b)=J₂(b), so that the I and Q componentshave the same amplitude. However, b depends on the distance L. Anembodiment may apply a triangle wave modulation to the VCSEL's biascurrent to determine a distance to a point of interest. Then thisdistance is used find the optimal peak-to-peak sinusoidal modulation ofthe bias current to use in an I/Q approach. Such a dual method approachmay provide improved signal-to-noise ratio and displacement accuracyobtained from the I/Q method.

Referring now to FIG. 11, there is shown an exemplary structural blockdiagram of components of an electronic device 1100, such as theembodiments described above. The block diagram is exemplary only;various embodiments described above may be implemented using otherstructural components and configurations. The electronic device 1100 caninclude one or more processors or processing unit(s) 1102, storage ormemory components 1104, a power source 1106, a display 1108 (which maydisplay or indicate an operating status, or display the image beingprojected in an AR/VR system), an input/output interface 1110, one ormore sensors such as microphones, a network communication interface1114, and one or more self-mixing interferometry (SMI) sensors 1112, asdescribed above. Either of the display 1108 or the input/outputinterface 1110 may include input touch screens, buttons, sliders,indicator lights, etc., by which a user can control operation of theelectronic device 1100. These various components will now be discussedin turn below.

The one or more processors or processing units 1102 can control some orall of the operations of the electronic device 1100. The processor(s)1102 can communicate, either directly or indirectly, with substantiallyall of the components of the electronic device 1100. In variousembodiments, the processing units 1102 may receive the self-mixinginterferometry signals from the SMI sensors 1112, such as self-mixinginterferometry signals from any or all of the photodetectors, VCSELs,and other electronics of the imaging and SMI sensors 1112. Such signalsmay include those that correspond to the interferometric parameters, andperform any of the methods, or parts of the methods, discussed above.

For example, one or more system buses 1118 or other communicationmechanisms can provide communication between the processor(s) orprocessing units 1102, the storage or memory components 1104 (or just“memory”), the power source 1106, the display 1108, the input/outputinterface 1110, the SMI sensor(s) 1112, the network communicationinterface 1114, and the microphone(s) 1116. The processor(s) orprocessing units 1102 can be implemented as any electronic devicecapable of processing, receiving, or transmitting data or instructions.For example, the one or more processors or processing units 1102 can bea microprocessor, a central processing unit (CPU), anapplication-specific integrated circuit (ASIC), a digital signalprocessor (DSP), or combinations of multiple such devices. As describedherein, the term “processor” or “processing unit” is meant to encompassa single processor or processing unit, multiple processors, multipleprocessing units, or other suitably configured computing element orelements.

The memory 1104 can store electronic data that can be used by theelectronic device 1100. For example, the memory 1104 can storeelectrical data or content such as, for example, audio files, documentfiles, timing signals, algorithms, and image data. The memory 1104 canbe configured as any type of memory. By way of example only, memory 1104can be implemented as random access memory, read-only memory, Flashmemory, removable memory, or other types of storage elements, in anycombination.

The power source 1106 can be implemented with any device capable ofproviding energy to the electronic device 1100. For the wearableelectronic devices described above, the power source 1106 can be abattery, such as a lithium, alkali, or other type.

The display 1108 may provide an image or video output for certain of theelectronic devices 1100, such as the AR/VR systems described above. Thedisplay 1108 can be any appropriate size for a wearable electronicdevice. The display 1108 may also function as a user touch inputsurface, in addition to displaying output from the electronic device1100. In these embodiments, a user may press on the display 1108 orgesture toward a portion of the image projected in the AR/VR system inorder to provide user input to the electronic device 1100. Such userinputs may be in addition to the user inputs based on the detection skindeformations and skin vibrations described above.

The input/output interface 1110 can be configured to allow a user toprovide settings or other inputs to the various embodiments describedabove. For example, the electronic device 1100 may include one or moreuser settable switches or buttons, such as to adjust a volume. Theinput/output interface 1110 may also be configured with one or moreindicator lights to provide a user with information related tooperational status of the electronic device.

In addition to the SMI sensors 1112, the electronic device 1100 mayinclude one or more microphones 1116, as described in relation to FIGS.2B-C. Examples of microphones include, but are not limited to,piezoelectric, condenser, ribbon, and other technologies known to oneskilled in the art.

The network communication interface 1114 can facilitate transmission ofdata to a user or to other electronic devices. For example, the networkcommunication interface 1114 can receive data from a network or send andtransmit electronic signals via a wireless connection. Examples ofwireless connections include, but are not limited to, Bluetooth, WiFi,or another technology. In one or more embodiments, the networkcommunication interface 1114 supports multiple network or communicationmechanisms. For example, the network communication interface 1114 canpair with another device over a Bluetooth network to transfer signals tothe other device while simultaneously receiving signals from a WiFi orother wired or wireless connection.

Other examples and implementations are within the scope and spirit ofthe disclosure and appended claims. For example, features implementingfunctions may also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. As used herein, the phrase “at least oneof” preceding a series of items, with the term “and” or “or” to separateany of the items, modifies the list as a whole, rather than each memberof the list. The phrase “at least one of” does not require selection ofat least one of each item listed; rather, the phrase allows a meaningthat includes at a minimum one of any of the items, and/or at a minimumone of any combination of the items, and/or at a minimum one of each ofthe items. By way of example, the phrases “at least one of A, B, and C”or “at least one of A, B, or C” each refer to only A, only B, or only C;any combination of A, B, and C; and/or one or more of each of A, B, andC. Similarly, it may be appreciated that an order of elements presentedfor a conjunctive or disjunctive list provided herein should not beconstrued as limiting the disclosure to only that order provided.Further, the term “exemplary” does not mean that the described exampleis preferred or better than other examples.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not targeted to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

What is claimed is:
 1. A wearable device, comprising: a frame configuredto attach the wearable device to a user; a self-mixing interferometrysensor mounted to the frame and configured to emit a beam of light; anda command interpreter configured to receive a self-mixing interferometrysignal from the self-mixing interferometry sensor; wherein: the frame isconfigured to direct the beam of light toward a head of the user; theself-mixing interferometry signal includes skin deformation information;and the command interpreter is configured to identify a command encodedin the skin deformation information.
 2. The wearable device of claim 1,wherein the skin deformation information includes skin vibrationinformation.
 3. The wearable device of claim 2, wherein the wearabledevice is an earbud further comprising: a microphone; and an in-earspeaker; and wherein: the self-mixing interferometry sensor directs thebeam of light toward a location in an ear of the user; and the commandinterpreter identifies a voiced command of the user using the skinvibration information.
 4. The wearable device of claim 2, wherein: thewearable device is an eyeglasses set; the self-mixing interferometrysensor is mounted to an arm of the eyeglasses set and directs the beamof light toward a location proximate to a temporal bone of the user; andthe command interpreter identifies a voiced command of the user based onthe skin vibration information.
 5. The wearable device of claim 1,wherein the skin deformation information includes temporomandibularjoint movement information.
 6. The wearable device of claim 5, wherein:the wearable device is a headphone; the self-mixing interferometrysensor directs the beam of light toward a location on the user's headproximate to a temporomandibular joint of the user; and the commandinterpreter identifies the temporomandibular joint movement informationas a silent gesture command of the user.
 7. The wearable device of claim5, wherein: the wearable device is a visual display headset; theself-mixing interferometry sensor is a first self-mixing interferometrysensor; the beam of light is a first beam of light; the self-mixinginterferometry signal is a first self-mixing interferometry signal; thefirst self-mixing interferometry sensor directs the beam of light towarda first location on the user's head proximate to a temporomandibularjoint of the user; the command interpreter identifies thetemporomandibular joint movement information as a silent gesture commandof the user; the wearable device comprises a second self-mixinginterferometry sensor that directs a second beam of light toward asecond location on the user's head proximate to a parietal bone; and thecommand interpreter is configured to receive a second self-mixinginterferometry signal from the second self-mixing interferometry sensor;wherein: the second self-mixing interferometry signal includes skinvibration information; and the command interpreter is configured toidentify a voiced command encoded in the skin vibration information. 8.The wearable device of claim 1, wherein: the beam of light is a laserlight beam emitted by a laser diode; a bias current of the laser diodeis modulated with a sine wave; and the command interpreter is configuredto use a time domain I/Q analysis to identify the command encoded in theskin deformation information.
 9. The wearable device of claim 1,wherein: the beam of light is a laser light emitted by a laser diode; abias current of the laser diode is modulated with a triangle wave; andthe command interpreter is configured to use a spectrum analysis toidentify the command encoded in the skin deformation information.
 10. Adevice, comprising: a head-mountable frame configured to be worn by auser; a self-mixing interferometry sensor mounted to the head-mountableframe and configured to emit a beam of light toward a location on theuser's head; a microphone; a command interpreter configured to receivean output of the microphone and recognize a voiced command of the user;and a bioauthentication circuit configured to authenticate the voicedcommand using a self-mixing interferometry signal of the self-mixinginterferometry sensor.
 11. The device of claim 10, wherein: theself-mixing interferometry signal includes skin deformation information;the bioauthentication circuit is operable to: detect, using at least theskin deformation information, that the user was speaking during a timeinterval of the received output of the microphone; and authenticate thevoiced command using the detection.
 12. The device of claim 11, whereinauthentication of the voiced command further includes detecting acorrelation of the voiced command of the user with a voice patterndetected in the skin deformation information.
 13. The device of claim10, wherein the device is an earbud further comprising: an in-earspeaker; and a radio transmitter; wherein: the device transmits thevoiced command using the radio transmitter upon authentication.
 14. Thedevice of claim 10, wherein: the device is a headphone; the location onthe user's head is proximate to at least one of a temporal bone and aparietal bone; and the device implements the voiced command uponauthentication.
 15. The device of claim 10, wherein: the beam of lightis a laser light beam emitted by a laser diode; the bioauthenticationcircuit is configured to authenticate the voiced command using at leastone of: a time domain I/Q analysis of the self-mixing interferometrysignal when a sine wave modulation is applied to a bias current of thelaser diode, and a spectrum analysis of the self-mixing interferometrysignal when a triangle wave modulation is applied to the bias current ofthe laser diode.
 16. A device, comprising: a head-mountable frameconfigured to be worn by a user; a self-mixing interferometry sensormounted to the head-mountable frame and configured to emit a beam oflight toward skin of the user; a microphone configured to produce anaudio signal; and an audio conditioning circuit configured to modify theaudio signal using a self-mixing interferometry signal of theself-mixing interferometry sensor.
 17. The device of claim 16, wherein:the self-mixing interferometry signal includes skin vibrationinformation; the audio conditioning circuit is configured to detect timeintervals of speech of the user using the skin vibration information;and modifying the audio signal includes suppressing background noiseduring a time segment not in the detected time intervals of speech ofthe user.
 18. The device of claim 17, wherein the device is an earbudfurther comprising: an in-ear speaker; and a radio transmitter; wherein:the device transmits the audio signal only during the detected timeintervals of speech of the user.
 19. The device of claim 17, wherein:the device is a headphone further comprising a radio transmitter; theself-mixing interferometry sensor directs the beam of light toward alocation on the user's head proximate to at least one of the temporalbone and the parietal bone; and the device transmits the audio signalonly during the detected time intervals of speech of the user.
 20. Thedevice of claim 16, wherein: the beam of light is a laser light beamemitted by a laser diode; the audio conditioning circuit is configuredto modify the audio signal using at least one of: a time domain I/Qanalysis of the self-mixing interferometry signal when a sine wavemodulation is applied to a bias current of the laser diode, and aspectrum analysis of the self-mixing interferometry signal when atriangle wave modulation is applied to the bias current of the laserdiode.